From: Felix Fietkau <nbd@nbd.name>
Date: Sat, 17 Feb 2018 11:49:44 +0100
Subject: [PATCH] netfilter: nf_flow_table: move ipv4 offload hook code to
 nf_flow_table

Allows some minor code sharing with the ipv6 hook code and is also
useful as preparation for adding iptables support for offload

Signed-off-by: Felix Fietkau <nbd@nbd.name>
---
 create mode 100644 net/netfilter/nf_flow_table_ip.c

--- a/net/ipv4/netfilter/nf_flow_table_ipv4.c
+++ b/net/ipv4/netfilter/nf_flow_table_ipv4.c
@@ -2,248 +2,8 @@
 #include <linux/init.h>
 #include <linux/module.h>
 #include <linux/netfilter.h>
-#include <linux/rhashtable.h>
-#include <linux/ip.h>
-#include <linux/netdevice.h>
-#include <net/ip.h>
-#include <net/neighbour.h>
 #include <net/netfilter/nf_flow_table.h>
 #include <net/netfilter/nf_tables.h>
-/* For layer 4 checksum field offset. */
-#include <linux/tcp.h>
-#include <linux/udp.h>
-
-static int nf_flow_nat_ip_tcp(struct sk_buff *skb, unsigned int thoff,
-			      __be32 addr, __be32 new_addr)
-{
-	struct tcphdr *tcph;
-
-	if (!pskb_may_pull(skb, thoff + sizeof(*tcph)) ||
-	    skb_try_make_writable(skb, thoff + sizeof(*tcph)))
-		return -1;
-
-	tcph = (void *)(skb_network_header(skb) + thoff);
-	inet_proto_csum_replace4(&tcph->check, skb, addr, new_addr, true);
-
-	return 0;
-}
-
-static int nf_flow_nat_ip_udp(struct sk_buff *skb, unsigned int thoff,
-			      __be32 addr, __be32 new_addr)
-{
-	struct udphdr *udph;
-
-	if (!pskb_may_pull(skb, thoff + sizeof(*udph)) ||
-	    skb_try_make_writable(skb, thoff + sizeof(*udph)))
-		return -1;
-
-	udph = (void *)(skb_network_header(skb) + thoff);
-	if (udph->check || skb->ip_summed == CHECKSUM_PARTIAL) {
-		inet_proto_csum_replace4(&udph->check, skb, addr,
-					 new_addr, true);
-		if (!udph->check)
-			udph->check = CSUM_MANGLED_0;
-	}
-
-	return 0;
-}
-
-static int nf_flow_nat_ip_l4proto(struct sk_buff *skb, struct iphdr *iph,
-				  unsigned int thoff, __be32 addr,
-				  __be32 new_addr)
-{
-	switch (iph->protocol) {
-	case IPPROTO_TCP:
-		if (nf_flow_nat_ip_tcp(skb, thoff, addr, new_addr) < 0)
-			return NF_DROP;
-		break;
-	case IPPROTO_UDP:
-		if (nf_flow_nat_ip_udp(skb, thoff, addr, new_addr) < 0)
-			return NF_DROP;
-		break;
-	}
-
-	return 0;
-}
-
-static int nf_flow_snat_ip(const struct flow_offload *flow, struct sk_buff *skb,
-			   struct iphdr *iph, unsigned int thoff,
-			   enum flow_offload_tuple_dir dir)
-{
-	__be32 addr, new_addr;
-
-	switch (dir) {
-	case FLOW_OFFLOAD_DIR_ORIGINAL:
-		addr = iph->saddr;
-		new_addr = flow->tuplehash[FLOW_OFFLOAD_DIR_REPLY].tuple.dst_v4.s_addr;
-		iph->saddr = new_addr;
-		break;
-	case FLOW_OFFLOAD_DIR_REPLY:
-		addr = iph->daddr;
-		new_addr = flow->tuplehash[FLOW_OFFLOAD_DIR_ORIGINAL].tuple.src_v4.s_addr;
-		iph->daddr = new_addr;
-		break;
-	default:
-		return -1;
-	}
-	csum_replace4(&iph->check, addr, new_addr);
-
-	return nf_flow_nat_ip_l4proto(skb, iph, thoff, addr, new_addr);
-}
-
-static int nf_flow_dnat_ip(const struct flow_offload *flow, struct sk_buff *skb,
-			   struct iphdr *iph, unsigned int thoff,
-			   enum flow_offload_tuple_dir dir)
-{
-	__be32 addr, new_addr;
-
-	switch (dir) {
-	case FLOW_OFFLOAD_DIR_ORIGINAL:
-		addr = iph->daddr;
-		new_addr = flow->tuplehash[FLOW_OFFLOAD_DIR_REPLY].tuple.src_v4.s_addr;
-		iph->daddr = new_addr;
-		break;
-	case FLOW_OFFLOAD_DIR_REPLY:
-		addr = iph->saddr;
-		new_addr = flow->tuplehash[FLOW_OFFLOAD_DIR_ORIGINAL].tuple.dst_v4.s_addr;
-		iph->saddr = new_addr;
-		break;
-	default:
-		return -1;
-	}
-
-	return nf_flow_nat_ip_l4proto(skb, iph, thoff, addr, new_addr);
-}
-
-static int nf_flow_nat_ip(const struct flow_offload *flow, struct sk_buff *skb,
-			  enum flow_offload_tuple_dir dir)
-{
-	struct iphdr *iph = ip_hdr(skb);
-	unsigned int thoff = iph->ihl * 4;
-
-	if (flow->flags & FLOW_OFFLOAD_SNAT &&
-	    (nf_flow_snat_port(flow, skb, thoff, iph->protocol, dir) < 0 ||
-	     nf_flow_snat_ip(flow, skb, iph, thoff, dir) < 0))
-		return -1;
-	if (flow->flags & FLOW_OFFLOAD_DNAT &&
-	    (nf_flow_dnat_port(flow, skb, thoff, iph->protocol, dir) < 0 ||
-	     nf_flow_dnat_ip(flow, skb, iph, thoff, dir) < 0))
-		return -1;
-
-	return 0;
-}
-
-static bool ip_has_options(unsigned int thoff)
-{
-	return thoff != sizeof(struct iphdr);
-}
-
-static int nf_flow_tuple_ip(struct sk_buff *skb, const struct net_device *dev,
-			    struct flow_offload_tuple *tuple)
-{
-	struct flow_ports *ports;
-	unsigned int thoff;
-	struct iphdr *iph;
-
-	if (!pskb_may_pull(skb, sizeof(*iph)))
-		return -1;
-
-	iph = ip_hdr(skb);
-	thoff = iph->ihl * 4;
-
-	if (ip_is_fragment(iph) ||
-	    unlikely(ip_has_options(thoff)))
-		return -1;
-
-	if (iph->protocol != IPPROTO_TCP &&
-	    iph->protocol != IPPROTO_UDP)
-		return -1;
-
-	thoff = iph->ihl * 4;
-	if (!pskb_may_pull(skb, thoff + sizeof(*ports)))
-		return -1;
-
-	ports = (struct flow_ports *)(skb_network_header(skb) + thoff);
-
-	tuple->src_v4.s_addr	= iph->saddr;
-	tuple->dst_v4.s_addr	= iph->daddr;
-	tuple->src_port		= ports->source;
-	tuple->dst_port		= ports->dest;
-	tuple->l3proto		= AF_INET;
-	tuple->l4proto		= iph->protocol;
-	tuple->iifidx		= dev->ifindex;
-
-	return 0;
-}
-
-/* Based on ip_exceeds_mtu(). */
-static bool nf_flow_exceeds_mtu(const struct sk_buff *skb, unsigned int mtu)
-{
-	if (skb->len <= mtu)
-		return false;
-
-	if ((ip_hdr(skb)->frag_off & htons(IP_DF)) == 0)
-		return false;
-
-	if (skb_is_gso(skb) && skb_gso_validate_mtu(skb, mtu))
-		return false;
-
-	return true;
-}
-
-unsigned int
-nf_flow_offload_ip_hook(void *priv, struct sk_buff *skb,
-			const struct nf_hook_state *state)
-{
-	struct flow_offload_tuple_rhash *tuplehash;
-	struct nf_flowtable *flow_table = priv;
-	struct flow_offload_tuple tuple = {};
-	enum flow_offload_tuple_dir dir;
-	struct flow_offload *flow;
-	struct net_device *outdev;
-	const struct rtable *rt;
-	struct iphdr *iph;
-	__be32 nexthop;
-
-	if (skb->protocol != htons(ETH_P_IP))
-		return NF_ACCEPT;
-
-	if (nf_flow_tuple_ip(skb, state->in, &tuple) < 0)
-		return NF_ACCEPT;
-
-	tuplehash = flow_offload_lookup(flow_table, &tuple);
-	if (tuplehash == NULL)
-		return NF_ACCEPT;
-
-	outdev = dev_get_by_index_rcu(state->net, tuplehash->tuple.oifidx);
-	if (!outdev)
-		return NF_ACCEPT;
-
-	dir = tuplehash->tuple.dir;
-	flow = container_of(tuplehash, struct flow_offload, tuplehash[dir]);
-	rt = (const struct rtable *)flow->tuplehash[dir].tuple.dst_cache;
-
-	if (unlikely(nf_flow_exceeds_mtu(skb, flow->tuplehash[dir].tuple.mtu)))
-		return NF_ACCEPT;
-
-	if (skb_try_make_writable(skb, sizeof(*iph)))
-		return NF_DROP;
-
-	if (flow->flags & (FLOW_OFFLOAD_SNAT | FLOW_OFFLOAD_DNAT) &&
-	    nf_flow_nat_ip(flow, skb, dir) < 0)
-		return NF_DROP;
-
-	flow->timeout = (u32)jiffies + NF_FLOW_TIMEOUT;
-	iph = ip_hdr(skb);
-	ip_decrease_ttl(iph);
-
-	skb->dev = outdev;
-	nexthop = rt_nexthop(rt, flow->tuplehash[!dir].tuple.src_v4.s_addr);
-	neigh_xmit(NEIGH_ARP_TABLE, outdev, &nexthop, skb);
-
-	return NF_STOLEN;
-}
-EXPORT_SYMBOL_GPL(nf_flow_offload_ip_hook);
 
 static struct nf_flowtable_type flowtable_ipv4 = {
 	.family		= NFPROTO_IPV4,
--- a/net/netfilter/Makefile
+++ b/net/netfilter/Makefile
@@ -113,7 +113,7 @@ obj-$(CONFIG_NFT_FWD_NETDEV)	+= nft_fwd_
 
 # flow table infrastructure
 obj-$(CONFIG_NF_FLOW_TABLE)	+= nf_flow_table.o
-nf_flow_table-objs := nf_flow_table_core.o
+nf_flow_table-objs := nf_flow_table_core.o nf_flow_table_ip.o
 
 obj-$(CONFIG_NF_FLOW_TABLE_INET) += nf_flow_table_inet.o
 
--- /dev/null
+++ b/net/netfilter/nf_flow_table_ip.c
@@ -0,0 +1,245 @@
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/netfilter.h>
+#include <linux/rhashtable.h>
+#include <linux/ip.h>
+#include <linux/netdevice.h>
+#include <net/ip.h>
+#include <net/neighbour.h>
+#include <net/netfilter/nf_flow_table.h>
+/* For layer 4 checksum field offset. */
+#include <linux/tcp.h>
+#include <linux/udp.h>
+
+static int nf_flow_nat_ip_tcp(struct sk_buff *skb, unsigned int thoff,
+			      __be32 addr, __be32 new_addr)
+{
+	struct tcphdr *tcph;
+
+	if (!pskb_may_pull(skb, thoff + sizeof(*tcph)) ||
+	    skb_try_make_writable(skb, thoff + sizeof(*tcph)))
+		return -1;
+
+	tcph = (void *)(skb_network_header(skb) + thoff);
+	inet_proto_csum_replace4(&tcph->check, skb, addr, new_addr, true);
+
+	return 0;
+}
+
+static int nf_flow_nat_ip_udp(struct sk_buff *skb, unsigned int thoff,
+			      __be32 addr, __be32 new_addr)
+{
+	struct udphdr *udph;
+
+	if (!pskb_may_pull(skb, thoff + sizeof(*udph)) ||
+	    skb_try_make_writable(skb, thoff + sizeof(*udph)))
+		return -1;
+
+	udph = (void *)(skb_network_header(skb) + thoff);
+	if (udph->check || skb->ip_summed == CHECKSUM_PARTIAL) {
+		inet_proto_csum_replace4(&udph->check, skb, addr,
+					 new_addr, true);
+		if (!udph->check)
+			udph->check = CSUM_MANGLED_0;
+	}
+
+	return 0;
+}
+
+static int nf_flow_nat_ip_l4proto(struct sk_buff *skb, struct iphdr *iph,
+				  unsigned int thoff, __be32 addr,
+				  __be32 new_addr)
+{
+	switch (iph->protocol) {
+	case IPPROTO_TCP:
+		if (nf_flow_nat_ip_tcp(skb, thoff, addr, new_addr) < 0)
+			return NF_DROP;
+		break;
+	case IPPROTO_UDP:
+		if (nf_flow_nat_ip_udp(skb, thoff, addr, new_addr) < 0)
+			return NF_DROP;
+		break;
+	}
+
+	return 0;
+}
+
+static int nf_flow_snat_ip(const struct flow_offload *flow, struct sk_buff *skb,
+			   struct iphdr *iph, unsigned int thoff,
+			   enum flow_offload_tuple_dir dir)
+{
+	__be32 addr, new_addr;
+
+	switch (dir) {
+	case FLOW_OFFLOAD_DIR_ORIGINAL:
+		addr = iph->saddr;
+		new_addr = flow->tuplehash[FLOW_OFFLOAD_DIR_REPLY].tuple.dst_v4.s_addr;
+		iph->saddr = new_addr;
+		break;
+	case FLOW_OFFLOAD_DIR_REPLY:
+		addr = iph->daddr;
+		new_addr = flow->tuplehash[FLOW_OFFLOAD_DIR_ORIGINAL].tuple.src_v4.s_addr;
+		iph->daddr = new_addr;
+		break;
+	default:
+		return -1;
+	}
+	csum_replace4(&iph->check, addr, new_addr);
+
+	return nf_flow_nat_ip_l4proto(skb, iph, thoff, addr, new_addr);
+}
+
+static int nf_flow_dnat_ip(const struct flow_offload *flow, struct sk_buff *skb,
+			   struct iphdr *iph, unsigned int thoff,
+			   enum flow_offload_tuple_dir dir)
+{
+	__be32 addr, new_addr;
+
+	switch (dir) {
+	case FLOW_OFFLOAD_DIR_ORIGINAL:
+		addr = iph->daddr;
+		new_addr = flow->tuplehash[FLOW_OFFLOAD_DIR_REPLY].tuple.src_v4.s_addr;
+		iph->daddr = new_addr;
+		break;
+	case FLOW_OFFLOAD_DIR_REPLY:
+		addr = iph->saddr;
+		new_addr = flow->tuplehash[FLOW_OFFLOAD_DIR_ORIGINAL].tuple.dst_v4.s_addr;
+		iph->saddr = new_addr;
+		break;
+	default:
+		return -1;
+	}
+
+	return nf_flow_nat_ip_l4proto(skb, iph, thoff, addr, new_addr);
+}
+
+static int nf_flow_nat_ip(const struct flow_offload *flow, struct sk_buff *skb,
+			  enum flow_offload_tuple_dir dir)
+{
+	struct iphdr *iph = ip_hdr(skb);
+	unsigned int thoff = iph->ihl * 4;
+
+	if (flow->flags & FLOW_OFFLOAD_SNAT &&
+	    (nf_flow_snat_port(flow, skb, thoff, iph->protocol, dir) < 0 ||
+	     nf_flow_snat_ip(flow, skb, iph, thoff, dir) < 0))
+		return -1;
+	if (flow->flags & FLOW_OFFLOAD_DNAT &&
+	    (nf_flow_dnat_port(flow, skb, thoff, iph->protocol, dir) < 0 ||
+	     nf_flow_dnat_ip(flow, skb, iph, thoff, dir) < 0))
+		return -1;
+
+	return 0;
+}
+
+static bool ip_has_options(unsigned int thoff)
+{
+	return thoff != sizeof(struct iphdr);
+}
+
+static int nf_flow_tuple_ip(struct sk_buff *skb, const struct net_device *dev,
+			    struct flow_offload_tuple *tuple)
+{
+	struct flow_ports *ports;
+	unsigned int thoff;
+	struct iphdr *iph;
+
+	if (!pskb_may_pull(skb, sizeof(*iph)))
+		return -1;
+
+	iph = ip_hdr(skb);
+	thoff = iph->ihl * 4;
+
+	if (ip_is_fragment(iph) ||
+	    unlikely(ip_has_options(thoff)))
+		return -1;
+
+	if (iph->protocol != IPPROTO_TCP &&
+	    iph->protocol != IPPROTO_UDP)
+		return -1;
+
+	thoff = iph->ihl * 4;
+	if (!pskb_may_pull(skb, thoff + sizeof(*ports)))
+		return -1;
+
+	ports = (struct flow_ports *)(skb_network_header(skb) + thoff);
+
+	tuple->src_v4.s_addr	= iph->saddr;
+	tuple->dst_v4.s_addr	= iph->daddr;
+	tuple->src_port		= ports->source;
+	tuple->dst_port		= ports->dest;
+	tuple->l3proto		= AF_INET;
+	tuple->l4proto		= iph->protocol;
+	tuple->iifidx		= dev->ifindex;
+
+	return 0;
+}
+
+/* Based on ip_exceeds_mtu(). */
+static bool nf_flow_exceeds_mtu(const struct sk_buff *skb, unsigned int mtu)
+{
+	if (skb->len <= mtu)
+		return false;
+
+	if ((ip_hdr(skb)->frag_off & htons(IP_DF)) == 0)
+		return false;
+
+	if (skb_is_gso(skb) && skb_gso_validate_mtu(skb, mtu))
+		return false;
+
+	return true;
+}
+
+unsigned int
+nf_flow_offload_ip_hook(void *priv, struct sk_buff *skb,
+			const struct nf_hook_state *state)
+{
+	struct flow_offload_tuple_rhash *tuplehash;
+	struct nf_flowtable *flow_table = priv;
+	struct flow_offload_tuple tuple = {};
+	enum flow_offload_tuple_dir dir;
+	struct flow_offload *flow;
+	struct net_device *outdev;
+	const struct rtable *rt;
+	struct iphdr *iph;
+	__be32 nexthop;
+
+	if (skb->protocol != htons(ETH_P_IP))
+		return NF_ACCEPT;
+
+	if (nf_flow_tuple_ip(skb, state->in, &tuple) < 0)
+		return NF_ACCEPT;
+
+	tuplehash = flow_offload_lookup(flow_table, &tuple);
+	if (tuplehash == NULL)
+		return NF_ACCEPT;
+
+	outdev = dev_get_by_index_rcu(state->net, tuplehash->tuple.oifidx);
+	if (!outdev)
+		return NF_ACCEPT;
+
+	dir = tuplehash->tuple.dir;
+	flow = container_of(tuplehash, struct flow_offload, tuplehash[dir]);
+	rt = (const struct rtable *)flow->tuplehash[dir].tuple.dst_cache;
+
+	if (unlikely(nf_flow_exceeds_mtu(skb, flow->tuplehash[dir].tuple.mtu)))
+		return NF_ACCEPT;
+
+	if (skb_try_make_writable(skb, sizeof(*iph)))
+		return NF_DROP;
+
+	if (flow->flags & (FLOW_OFFLOAD_SNAT | FLOW_OFFLOAD_DNAT) &&
+	    nf_flow_nat_ip(flow, skb, dir) < 0)
+		return NF_DROP;
+
+	flow->timeout = (u32)jiffies + NF_FLOW_TIMEOUT;
+	iph = ip_hdr(skb);
+	ip_decrease_ttl(iph);
+
+	skb->dev = outdev;
+	nexthop = rt_nexthop(rt, flow->tuplehash[!dir].tuple.src_v4.s_addr);
+	neigh_xmit(NEIGH_ARP_TABLE, outdev, &nexthop, skb);
+
+	return NF_STOLEN;
+}
+EXPORT_SYMBOL_GPL(nf_flow_offload_ip_hook);
